The top-ranked doubles players make a solid living and Jamie Murray is no exception, being a two-time Grand Slam winner and a five-time Grand Slam mixed doubles champion himself. The majority of doubles players have quit playing the singles tournaments. However, there are still singles players entering the doubles matches simultanously and Jamie can't always appreciate that.
When Murray spoke to Behind the Racquet he aired his feelings on the subject: "I find it interesting when the singles guys compete against doubles. It’s fun watching these contrasting styles of tennis on the same court. The singles guys might rip on the doubles guys but at the end of the day, they’re still out there competing each week because it’s way for them to make basically stress free money."
“You just sign your name every week, doesn’t matter if you win, lose or draw and there’s no accountability for their performance. Whereas for doubles guys if I lose four times in a row, my ranking is going to drop and I won’t get into any tournaments. For the singles guys, it doesn’t matter what the results are they can just keep signing in."
“I do find it frustrating, and not a good look for our product, if there are guys on court playing without any interest of trying to win. They’re just there to get a little practice in, get used to the conditions and a quick paycheck. Since the money continues to grow in tennis, the whole pie is getting bigger."
https://twitter.com/jamie_murray/status/1198709921547726848